CYP2C9 Allelic Variants Research Articles

French-Speaking Network of Pharmacogenetics (RNPGx) Recommendations for Clinical Use of Mavacamten.

Mavacamten, the first drug in the class of β-cardiac myosin modulator, is used for the treatment of patients with hypertrophic cardiomyopathy. This orally administered drug demonstrates wide interpatient variability in pharmacokinetics parameters, due in part to variant CYP2C19 alleles. Individuals who are CYP2C19 poor metabolizers have increased exposure and are at increased risk of reduced cardiac hypercontractility. To ensure the safety of all patients, European Medicines Agency recommends CYP2C19 preemptive genotyping, and consecutively, to adapt maintenance and initial mavacamten doses, and to manage drug-drug interactions, according to CYP2C19 phenotype. In this article, we summarize evidence from the literature supporting the association between CYP2C19 phenotype and pharmacological features of mavacamten and provide, beyond biologic guidelines, therapeutic recommendations for the use of mavacamten based on CYP2C19 and CYP3A4/CYP3A5 genotype.

Clopidogrel Resistance in Ischemic Stroke Patients.

Stroke remained the second leading cause of death globally in 2019. The antiplatelet drug clopidogrel is used to keep blood clots from forming in people who have experienced a stroke. Although most people find clopidogrel to be safe and beneficial, there is inevitably a range in how each patient responds. The review covers about Clopidogrel resistance in stroke patients, their risk factors and the methods to identify it. Clopidogrel resistance is characterized as the drug's inability to prevent the target enzyme from acting. The prognosis of patients with ischemic stroke and the responsiveness to clopidogrel are significantly impacted by the various genetic polymorphism CYP2C19 genotypes. The two primary mutant alleles, CYP2C19 *2 and CYP2C19 *3, have been found to be the most prevalent genotypes. Better mRS scores six months after treatment showed a higher response rate in patients without these CYP2C19 variant alleles. Other factors are drug-drug interaction (proton pump inhibitors), demographics (age, sex, social history), comorbid conditions, etc. Blood samples for testing platelet reactivity were drawn one month after discharge from a peripheral blood sample. Several methods are used to identify the clopidogrel resistance. Some of them are ADP-Induced platelet aggregation, Platelet Reactivity Index VASP, Verify Now Assay, TEG Analyzer, Plasma microRNA-223. Drugs that are not prodrugs and whose metabolism is not dependent upon CYP2C19 can be selected as a superior alternative in case of CR. Ticagrelor is one such effective substitute. Proton pump inhibitors and clopidogrel should only be used concurrently in patients with reliable clinical indications.

Efficacy of P2Y12 receptor inhibitors in myocardial infarction in individuals carrying different CYP2C19 genotypes living in the northern region of Russia

Aim. To evaluate the efficacy of P2Y12 receptor inhibitors (clopidogrel and ticagrelor) in patients with myocardial infarction (MI) living in the northern region of Russia (Khanty-Mansi Autonomous Okrug — Yugra), depending on the carriage of various CYP2C19 allelic variants.Material and methods. This prospective observational study included 218 patients with acute MI who underwent percutaneous coronary intervention (PCI). The patients also underwent determination of allelic variants of the CYP2C19 gene. Patient were divided into groups receiving clopidogrel (n=164, 75%) and ticagrelor (n=54, 25%). Using biostatistical analysis methods, a comparison of clinical and genetic characteristics was performed, as well as an assessment of the risk of ischemic events between the groups in the long-term (108 months, 9 years) post-infarction period.Results. Reduced (*1/*2, *2/*2, *1/*3) and increased (*1/*17, *17/*17) metabolizer CYP2C19 genotypes, as well as severe comorbidity, are reliable independent predictors of composite outcome (cardiovascular death, recurrent acute coronary syndrome, coronary stent/bypass thrombosis, myocardial revascularization, acute ischemic cerebrovascular accident) during a long-term (9 years) follow-up. The advantages of ticagrelor over clopidogrel in terms of the effect on the incidence of ischemic events in the long-term period were established without a significant difference for bleeding both in the general cohort of patients and among carriers of CYP2C19 allelic variants (*1/*2, *2/*2, *1/*3) and (*1/*17,*17/*17) in patients with MI.Conclusion. Ticagrelor is significantly more effective than clopidogrel in reducing the risk of ischemic events in the general cohort of patients, as well as in carriers of reduced (*1/*2, *2/*2, *1/*3) and increased (*1/*17, *17/*17) metabolizer CYP2C19 genotypes during 9-year follow-up after the index MI.

Pharmacogenetics: Influence of CYP2C9*2 and *3 alleles polymorphisms on Iraqi type 2 diabetic patients

Abstract Background: Sulfonylureas (SUs) are the most prescribed anti-diabetic drugs. The enzyme responsible for metabolizing of SUs is hepatic cytochrome P4502C9 (CYP2C9). The CYP2C9 gene has numerous allelic variations; among those, the CYP2C9*2 and CYP2C9*3 are the most common and clinically significant allelic variations. The pharmacokinetics of SUs are dramatically impacted by CYP2C9 genotype. Objective: Evaluation of the association of genetic polymorphisms in CYP2C9 gene with the efficacy of glibenclamide (GB), second-generation SUs, by investigating two CYP2C9 allelic variants. Materials and Methods: Blood samples were collected from 113 type 2 diabetes patients. Allele specific amplification-polymerase chain reaction was used to genotype the CYP2C9 gene. Fasting serum glucose, fasting insulin, and glycated hemoglobin (HbA1c) levels were measured as part of the biochemical analysis. Results: The CYP2C9 gene variants were analyzed in a study group. The results exposed that 75 patients carried the wild (CYP2C9*1/*1) genotype, 25 were heterozygote allele (CYP2C9*1/*2) for CYP2C9*2 gene, 4 were homozygous for the variant CYP2C9*2 allele (CYP2C9*2/*2), and 9 were heterozygous for the variant CYP2C9*3 allele (CYP2C9*1/*3). Statistically significant difference was found in mean HbA1c between the mutant and wild alleles group (P = 0.044). The mean HbA1c for those carrying the CYP2C9*2 and*3 alleles (n = 38) was 8.4750 compared to 9.3177 for those carrying the CYP2C9*1 allele (n = 75), which indicate better glycemic control. Conclusion: The accordance of CYP2C9*2 and*3 was found to be associated with severe hypoglycemia (odd ratio [OR] = 2.045). The OR suggests a strong association between CYP2C9*2 and*3 alleles and hypoglycemia. Our findings imply that the diabetic patients with CYP2C9 polymorphism are more likely to suffer hypoglycemia than those with wild type alleles when treated with GB.

Association of CYP2C9*2 Allele with Sulphonylurea-Induced Hypoglycaemia in Type 2 Diabetes Mellitus Patients: A Pharmacogenetic Study in Pakistani Pashtun Population.

Polymorphism in cytochrome P450 (CYP) 2C9 enzyme is known to cause significant inter-individual differences in drug response and occurrence of adverse drug reactions. Different alleles of the CYP2C9 gene have been identified, but the notable alleles responsible for reduced enzyme activity are CYP2C9*2 and CYP2C9*3. No pharmacogenetic data are available on CYP2C9*2 and CYP2C9*3 alleles in the Pakistani population. In Pakistan, pharmacogenetics, which examines the relationship between genetic factors and drug response, are in the early stages of development. We, for the first time, investigated the association between the CYP2C9 variant alleles CYP2C9*2 and CYP2C9*3 and the incidence of hypoglycaemia in patients with Type 2 diabetes mellitus (T2DM) receiving sulphonylurea medications. A total of n = 400 individuals of Pashtun ethnicity were recruited from 10 different districts of Khyber Pakhtunkhwa, Pakistan to participate in the study. The study participants were divided into two distinct groups: the case group (n = 200) and the control group (n = 200). The case group consisted of individuals with T2DM who were receiving sulphonylurea medications and experienced hypoglycaemia with it, whereas the control group included individuals with T2DM who were receiving sulphonylurea medication but did not experience sulphonylurea-induced hypoglycaemia (SIH). Blood samples were obtained from study participants following informed consent. DNA was isolated from whole blood samples using a Wiz-Prep DNA extraction kit. Following DNA isolation, CYP2C9 alleles were genotyped using MassARRAY sequencing platform at the Centre of Genomics at the Rehman Medical Institute (RMI). The frequency of CYP2C9*2 (low-activity allele) was more frequent in the diabetic patients with SIH compared to the control group (17.5% vs. 6.0%, p = 0.021). The frequency of its corresponding genotype CYP2C9*1/*2 was higher in cases compared to the control group (10% vs. 6% with p = 0.036); the same was true for genotype CYP2C9*2/*2 (7% vs. 3.5% with p = 0.028). Logistic regression analysis evidenced potential association of CYP2C9*2 allele and its genotypes with SIH. When adjusted for confounding factors such as age, weight, sex, mean daily dose of sulphonylurea, and triglyceride level, the association between the CYP2C9*2 allele and hypoglycaemia remained consistent. Confounding factors played no role in SIH (insignificant p-value) because both groups (cases and controls) were closely matched in term of age, weight, sex, mean daily dose of sulphonylurea, and triglyceride levels. Our study suggests that genetic information about a patient's CYP2C9 gene/enzyme can potentially assist physicians in prescribing the most suitable and safest drug, based on their genetic make-up.

Effects of elagolix on the pharmacokinetics of omeprazole and its metabolites in healthy premenopausal women.

This study evaluated the effect of repeated doses of elagolix on the pharmacokinetics (PK) of omeprazole and its metabolites in healthy premenopausal female subjects. Adult premenopausal female subjects (N = 20) received a single oral dose of omeprazole (40 mg) on day 1 and day 11 and oral doses of elagolix (300 mg) twice‐daily on days 3–11. Serial blood samples for assay of omeprazole and its metabolites were collected for 24 h after dosing on days 1 and 11. PK parameters were calculated for omeprazole, 5‐hydroxyomeprazole and omeprazole sulfone; and were compared between day 1 and day 11. Pharmacogenetic testing was performed for CYP2C19 variant alleles and the results were used to compare the magnitude of elagolix–omeprazole drug–drug interaction (DDI) between the different genotype subgroups. Administration of elagolix 300 mg twice‐daily for 9 days increased omeprazole exposure by 1.8‐fold and decreased the metabolite‐to‐parent ratio for 5‐hydroxyomeprazole by ~60%. Conversely, there was an increase in the metabolite‐to‐parent ratio for omeprazole sulfone by 25%. Elagolix increased omeprazole exposures by 2‐ to 2.5‐fold in CYP2C19 extensive (EM) and intermediate (IM) metabolizer subjects, but decreased omeprazole exposures by 40% in poor metabolizer subjects. Exposures of 5‐hydroxyomeprazole decreased by 20%–30% in all genotype subgroups, and omeprazole sulfone exposures increased by ~3‐fold in EM and IM subjects. Elagolix is a weak inhibitor of CYP2C19 and exposure of CYP2C19 substrates may be increased upon coadministration with elagolix. Omeprazole may exhibit drug interactions due to multiple mechanisms other than CYP2C19‐mediated metabolism; complicating the interpretation of results from omeprazole DDI studies.

DO VKORC1 AND CYP2C9 MUTATIONS LEAD TO WARFARIN RESISTANCE?

The objective of this study was to determine the influence of VKORC1 and CYP2C9 polymorphisms on warfarin resistant patients. Warfarin resistance is described as the inability to prolong the prothrombin time or raise the INR up to the 2 therapeutic range when the drug is given at typically doses. Polymorphisms may play a role as some VKORC1 and CYP2C9 variant alleles are known to be associated with these circumstances. 28 patients who were taking warfarin more than 15 mg/day and had INR values below 2.1 and had thromboembolic events while using warfarin were enrolled in this study. Heterozygote mutation in the VKORC1 gene was identified in 15 of 28 patients. Seven patients had heterozygote mutation of the CYP2C9 gene, and that may correspond to the ultrarapid metabolism of warfarin. VKORC1 and CYP2C9 polymorphism contribute to the difference in dose requirement amongst the patients, but other additional possible factors may play a role in different races. We suggest that medicians may use this tests before starting warfarin therapy and shape the treatment course according to this results.

Genetic and Nongenetic Determinants of Variable Warfarin Dose Requirements: A Report from North India

Introduction: Warfarin is widely used and will continue to be prescribed especially in developing countries due to its low cost. Given the huge patient load requiring anticoagulation, there is a need to develop strategies to optimize warfarin therapy for ensuring safe and effective anticoagulation. In the present work, we aimed at elucidating the association of genetic and nongenetic variables with warfarin dose requirement in patients attending the cardiovascular clinic in a tertiary care center of North India. Methods: This was a prospective study conducted over 1 year. Patient demographic and clinical details were captured in customized case record forms. Genotyping was done using the polymerase chain reaction-restriction fragment length polymorphism method. Pharmacogenetic influence of CYP2C9 (rs1799853 and rs1057910) and VKORC1 (rs9923231) variant alleles was studied. The association of genetic and nongenetic factors with warfarin dose was quantified using a stepwise multivariate linear regression model. Results: Two hundred and forty patients were screened. Data from 82 eligible patients were used for quantifying the association of genetic and nongenetic factors with warfarin dose. A descriptive model based on CYP2C9*3 (rs1057910) and VKORC1 (rs9923231) variant alleles and BMI was developed. The model explains nearly half of the interindividual variation in warfarin dose requirement. Conclusion: The model explains nearly half of the interindividual variation in warfarin dose in patients with atrial fibrillation and or requiring valve replacement.

The influence of CYP2C19*2 and CYP3A5*3 variants on the development of depression and effectiveness of therapy: A preliminary study

The most common mental illness is depression; however, its pathogenesis is not fully understood. One of the factors that may influence its development and the effectiveness of therapy are the cytochromes of the p450 complex. CYP3A5 and CYP2C19 are involved in the metabolism of drugs used in the treatment of depression. These cytochromes can also generate reactive oxygen species, which are known to participate in the pathogenesis of depression. The aim of the study was to determine the frequency of CYP3A5*3 and CYP2C19*2 variants among a group of patients with depression to identify any potential association with disease development and progression, and the effectiveness of pharmacotherapy. A group of 103 patients suffering from recurrent depressive disorder and another of 93 healthy individuals were investigated using RFLP. It was found that the CYP3A5*3 allele may have a protective role in the development of depression (p = 0.0036). Heterozygous CYP3A5*1/*3 was more common in controls than the patients (p = 0.0300). Homozygotes were associated with an earlier onset than heterozygotes (p = 0.0292). For CYP2C19, patients with at least one CYP2C19*2 allele revealed better treatment results expressed as percentage change in Hamilton Depression Rating Scale (p = 0.0239). The identification of CYP3A5 and CYP2C19 allelic variants may be useful when assessing the effectiveness of pharmacotherapy.

Association Between the CYP2C9 Genotype and Hypoglycemia Among Patients With Type 2 Diabetes Receiving Sulfonylurea Treatment: A Meta-analysis

PurposeTwo common variants, CYP2C9*2 (Arg144Cys, rs1799853) and CYP2C9*3 (Ile359Leu, rs1057910), are known to reduce the catalytic function of the CYP2C9 enzyme. Because impaired catalytic function is likely to affect sulfonylurea metabolism, it is predictable that CYP2C9 loss-of-function alleles may increase the risk of sulfonylurea-induced hypoglycemia. This systematic review and meta-analysis aimed to assess the association between CYP2C9 genotype and hypoglycemia among patients with type 2 diabetes mellitus (T2DM) receiving sulfonylurea. MethodsWe searched for studies on the association between CYP2C9 genotype and sulfonylurea-induced hypoglycemia among patients with T2DM, published through August 7, 2020, using PubMed, Web of Science, and EMBASE. Odds ratios (ORs) and 95% CIs were calculated. FindingsFive cohort studies and 2 case-control studies were included, and the total number of patients analyzed in this meta-analysis was 2769. The CYP2C9 variant alleles were associated with an increase in sulfonylurea-induced hypoglycemia compared with wild-type homozygote (OR = 1.24; 95% CI, 1.03–1.48). Compared with CYP2C9 wild-type homozygotes, CYP2C9*2 allele was associated with increased incidence of hypoglycemia (OR = 1.85; 95% CI, 1.18–2.89), whereas the CYP2C9*3 allele failed to show the statistical significance (OR = 1.67; 95% CI, 0.40–6.86; P = 0.48). ImplicationsOn the basis of these results, CYP2C9 genotyping may be useful for predicting the risk of hypoglycemia during sulfonylurea treatment for T2DM.

CYP2C19 Polymorphisms in Indonesia: Comparison among Ethnicities and the Association with Clinical Outcomes.

Simple SummaryCYP2C19 is known as an enzyme primarily responsible for metabolizing various drugs, such as proton pump inhibitor, antiplatelet, anti-epileptic, and anticoagulant. CYP2C19 is known to be polymorphic and can result in the clinical efficacy of drugs. To examine the prevalence and the distribution of the CYP2C19 genetic polymorphisms in Indonesia, we performed polymerase chain reaction-restriction fragment length polymorphism to the genomic DNA of Indonesian participants. In addition, we also analyzed the distribution of CYP2C19 polymorphisms among ethnicities and clinical outcomes. We found that the prevalence of intermediate metabolizers were the highest in Indonesia, followed by rapid metabolizers and poor metabolizers, respectively. The distribution of metabolizer groups were different between ethnic groups in Indonesia. Therefore, dosage adjustment should be considered when administering drugs-affected by CYP2C19 in Indonesia. The results presented in this study showed the distribution of CYP2C19 variant alleles at the population level in Indonesia and might be used as a consideration for providing personalized treatment in clinical practice.CYP2C19 polymorphisms are important factors for proton pump inhibitor-based therapy. We examined the CYP2C19 genotypes and analyzed the distribution among ethnicities and clinical outcomes in Indonesia. We employed the polymerase chain reaction-restriction fragment length polymorphism method to determine the CYP2C19 genotypes and evaluated inflammation severity with the updated Sydney system. For CYP2C19*2, 46.4% were the homozygous wild-type allele, 14.5% were the homozygous mutated allele, and 39.2% were the heterozygous allele. For CYP2C19*3, 88.6% were the homozygous wild-type allele, 2.4% were the homozygous mutated allele, and 9.0% were the heterozygous allele. Overall, the prevalence of rapid, intermediate, and poor metabolizers in Indonesia was 38.5, 41.6, and 19.9%, respectively. In the poor metabolizer group, the frequency of allele *2 (78.8%) was higher than the frequency of allele *3 (21.2%). The Papuan had a significantly higher likelihood of possessing poor metabolizers than the Balinese (OR 11.0; P = 0.002). The prevalence of poor metabolizers was lower compared with the rapid and intermediate metabolizers among patients with gastritis and gastroesophageal reflux disease. Intermediate metabolizers had the highest prevalence, followed by rapid metabolizers and poor metabolizers. Dosage adjustment should therefore be considered when administering proton pump inhibitor-based therapy in Indonesia.

Influence of CYP2C9, VKORC1, and CYP4F2 polymorphisms on the pharmacodynamic parameters of warfarin: a cross-sectional study.

Warfarin is the most commonly evaluated drug in pharmacogenetic-guided dosing studies. However, gaps remain regarding the influence of the genetic polymorphisms of CYP2C9, VKORC1, and CYP4F2 on specific pharmacodynamic parameters like the warfarin sensitivity index (WSI), prothrombin time international normalized ratio (PT-INR), and log-INR variability. A cross-sectional study was conducted in non-smoking adults receiving warfarin for at least 6months. Their demographics, diagnoses, warfarin dosing regimen, concomitant drugs, PT-INR, and bleeding episodes were obtained. CYP2C9 (rs1057910-*3 and rs1799853-*2 alleles), CYP4F2 (rs2108622), and VKORC1 (rs9923231) polymorphisms were assessed using real-time polymerase chain reaction. Three genotype groups (I-III) were defined based on the combined genetic polymorphisms of CYP2C9 and VKORC1 from the FDA's recommendations. Key outcome measures included anticoagulation control, time spent in therapeutic range, stable warfarin dose, WSI, log-INR variability, and Warfarin Composite Measure (WCM). The study recruited 236 patients; 75 (31.8%) carried a functional CYP2C9 variant allele, and, 143 (60.6%) had at least one T allele in CYP4F2 and 133 (56.4%) had at least one T allelein VKORC1. Groups' II and III CYP2C9 and VKORC1 genotypes were observed with reduced stable warfarin dose, increased WSI, higher log-INR variability, and increased bleeding risk. The presence of *2 or *3 allele in CYP2C9 was observed with reduced stable warfarin doses akin to the presence of T alleles in VKORC1; however, the doses increased with T alleles in CYP4F2. The evaluated genetic polymorphisms significantly influenced all the pharmacodynamic parameters of warfarin. Evaluating CYP2C9, VKORC1, and CYP4F2 genetic polymorphisms prior to warfarin initiation is likely to optimize therapeutic response.

Pharmacogenetic algorithm for predicting daily dose of warfarin in Caucasian patients of Czech origin

Abstract Objectives Warfarin use is limited by a low therapeutic index and significant interindividual variability of the daily dose. The most important factor predicting daily warfarin dose is individual genotype, polymorphisms of genes CYP2C9 (warfarin metabolism) and VKORC1 (sensitivity for warfarin). Algorithms using clinical and genetic variables could predict the daily dose before the initiation of therapy. The aim of this study was to develop and validate an algorithm for the prediction of warfarin daily dose in Czech patients. Methods Detailed clinical data of patients with known and stable warfarin daily dose were collected. All patients were genotyped for polymorphisms in genes CYP2C9 and VKORC1. Results Included patients were divided into derivation (n=175) and validation (n=223) cohorts. The final algorithm includes the following variables: Age, height, weight, treatment with amiodarone and presence of variant alleles of genes CYP2C9 and VKORC1. The adjusted coefficient of determination is 72.4% in the derivation and 62.3% in the validation cohort (p<0.001). Conclusions Our validated algorithm for warfarin daily dose prediction in our Czech cohort had higher precision than other currently published algorithms. Pharmacogenetics of warfarin has the potential in the clinical practice in specialized centers.

Pharmacogenetic algorithm for predicting daily dose of warfarin in Caucasian patients of Czech origin.

Warfarin use is limited by a low therapeutic index and significant interindividual variability of the daily dose. The most important factor predicting daily warfarin dose is individual genotype, polymorphisms of genes CYP2C9 (warfarin metabolism) and VKORC1 (sensitivity for warfarin). Algorithms using clinical and genetic variables could predict the daily dose before the initiation of therapy. The aim of this study was to develop and validate an algorithm for the prediction of warfarin daily dose in Czech patients. Detailed clinical data of patients with known and stable warfarin daily dose were collected. All patients were genotyped for polymorphisms in genes CYP2C9 and VKORC1. Included patients were divided into derivation (n=175) and validation (n=223) cohorts. The final algorithm includes the following variables: Age, height, weight, treatment with amiodarone and presence of variant alleles of genes CYP2C9 and VKORC1. The adjusted coefficient of determination is 72.4% in the derivation and 62.3% in the validation cohort (p<0.001). Our validated algorithm for warfarin daily dose prediction in our Czech cohort had higher precision than other currently published algorithms. Pharmacogenetics of warfarin has the potential in the clinical practice in specialized centers.

Comparison of CYP2C9 Activity in Ethiopian and Non-Ethiopian Jews Using Phenytoin as a Probe.

The pharmacokinetics of CYP2C9 substrates is characterized by substantial interethnic variability. The objective of the study was to compare CYP2C9 activity by using Phenytoin Metabolic Ratio (PMR) between Ethiopian and non-Ethiopian Jews. PMR was derived from the ratio of p-HPPH in 24 h urine collection to plasma phenytoin, 12 h (PMR24/12) or 24 h (PMR24/24) after the administration of 300 mg phenytoin. Analysis of CYP2C9*2, *3, *5, *6, *8, and *11 was carried by direct sequencing. PMR was significantly correlated with CYP2C9 genotype in both groups (p < 0.002). Mean PMR values were similar among Ethiopians and non-Ethiopians despite the fact that the fraction of non-carriers of CYP2C9 variant alleles was significantly different (85 vs. 53%, respectively, p < 0.001). However, among non-carriers of CYP2C9*2, *3, *5, *6, *8, and *11 variant alleles, PMR24/12 and PMR24/24 values were 30 and 34% greater respectively in the non-Ethiopians group (p < 0.001). In conclusion—CYP2C9 activity as measured by PMR is similar in Ethiopian and non-Ethiopian Jews. However, among non-carriers of CYP2C9 variant alleles accounting for 85% of Ethiopian Jews, CYP2C9 activity is decreased by approximately one third as compared with non-Ethiopian Jews. Unique genetic CYP2C9 polymorphisms occurring only in Ethiopians may account for this difference.

Validation of an algorithm to predict decline in INR following warfarin cessation in patients undergoing invasive procedures

Patients on warfarin are required to withdraw from treatment for a fixed period (normally 5 days) prior to an invasive procedure. However, the anticoagulant effect of warfarin subsides at different rates among different patients, exposing some to increased risk of either thrombosis or bleeding. In a recent study in patients awaiting surgery, following warfarin cessation the INR declined slower over time in those with two CYP2C9 variant alleles, increasing age, weight and number of comorbidities and that INR decline was faster in those with higher maintenance INR value. Subsequently, we developed an algorithm which predicts INR decline in individual patients after 5 days of warfarin cessation. The current study validated the algorithm. An independent cohort of patients completing a short course of warfarin took part in the study. INR values for subsequent 9 days and CYP2C9 genotype were available. The predicted INR decline (INRday 1–INRday 5) was compared to the observed one (where an INR check on day 5 was unavailable, INR was estimated using a linear approximation model). There was a strong correlation between the decline in INR by day 5 and that predicted from the algorithm for the 117 patients (r = 0.949, p < 0.001). The algorithm was precise, with low degree of bias and variance of the prediction error. The algorithm can accurately predict the INR decline following warfarin cessation in individual adult patients. The use of this easily adoptable algorithm can reduce cancellation or delays of planned surgical procedures.

Abstract LB-B19: Investigating the effect of pharmacogenetic variations on voriconazole levels in pediatric cancer patients

Abstract Background: Voriconazole is a second-generation triazole antifungal with broad-spectrum activity against Aspergillosis, metabolized mainly by CYP2C19 in the liver. Despite the use of weight-based dosing, plasma voriconazole blood levels show inter-individual variability, which is attributed to many factors such as weight, age, food, drug interactions, and CYP2C19 polymorphism. Voriconazole metabolism in pediatrics has been reported to be profoundly impacted by CYP2C19 genotypes. Aim: To evaluate the frequencies of CYP2C19 variant alleles (*2, *3, and *17), genotypes, and phenotypes in Egyptian pediatric cancer patients and to investigate the correlation between CYP2C19 genetic variability and other factors with voriconazole plasma levels. Methods: This study was conducted on 100 pediatric cancer patients with probable fungal infection treated with voriconazole. DNA was extracted from blood samples and analyzed by the TaqMan SNP genotyping assay. Identified genotypes were classified accordingly into various predicted phenotypes. Results: Voriconazole plasma levels widely varied, with only 49.5% reaching therapeutic levels. Frequencies of CYP2C19*2 and *17 allelic variants were 10.6 and 18.3%, respectively, while allele *3 was not detected in the study population. A significant correlation was found between plasma levels and CYP2C19 phenotypes: ultra-rapid metabolizers had significantly lower plasma levels (P=0.003) relative to the extensive metabolizer genotype. Conclusion: Determination of CYP2C19 genotype at initiation of therapy, followed by drug monitoring, would serve as a valuable tool for the optimization of voriconazole therapy for pediatric cancer patients. It would also be an essential step in the advancement of precision medicine to optimize therapeutic efficacy and minimize toxicity. Citation Format: Dina Saeed, Lobna Shalaby, Mohamed Nagy, Ahmed ElZeiny, Tarek M. Mostafa, Marwa T. ElRakaiby, Mohammed M. Nooh, Alaa El-Haddad, Maggie Abbassi, Ramy K. Aziz. Investigating the effect of pharmacogenetic variations on voriconazole levels in pediatric cancer patients [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference on Molecular Targets and Cancer Therapeutics; 2019 Oct 26-30; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2019;18(12 Suppl):Abstract nr LB-B19. doi:10.1158/1535-7163.TARG-19-LB-B19

AKR1D1*36 C>T (rs1872930) allelic variant is associated with variability of the CYP2C9 genotype predicted pharmacokinetics of ibuprofen enantiomers - a pilot study in healthy volunteers.

The relative contribution of CYP2C9 allelic variants to the pharmacokinetics (PK) of ibuprofen (IBP) enantiomers has been studied extensively, but the potential clinical benefit of pharmacogenetically guided IBP treatment is not evident yet. The role of AKR1D1*36C>T (rs 1872930) allelic variant in interindividual variability of CYP450 mediated drug metabolism was recently elucidated. A total of 27 healthy male subjects, volunteers in IBP single-dose two-way cross-over bioequivalence studies were genotyped for CYP2C9*2, CYP2C9*3 and AKR1D1*36 polymorphisms. The correlation between CYP2C9 and AKR1D1 genetic profile and the PK parameters for S-(+) and R-(-)-IBP was evaluated. Remarkable changes in the PK values pointing to reduced CYP2C9 enzyme activity were detected only in the CYP2C9*2 allelic variant carriers. Statistically significant association between the AKR1D1*36 allele and the increased IBP metabolism (low AUC0-t and 0-∞, high Cltot and short tmax values for both enantiomers) was observed in subjects carrying the CYP2C9 *1/*3 or CYP2C9*1/*1 genotype. The clinical value of concomitant CYP2C9 and AKR1D1 genotyping has to be further verified.

Frequency of CYP2C9 (*2, *3 and IVS8-109A>T) allelic variants, and their clinical implications, among Mexican patients with diabetes mellitus type 2 undergoing treatment with glibenclamide and metformin.

The majority of Mexican patients with diabetes mellitus type 2 (DMT2) (67.9-85.0%) are prescribed sulphonylureas (SUs), which are metabolized by cytochrome P450 2C9 (abbreviated as CYP2C9). SUs are a type of oral anti-diabetic compound which inhibit ATP-sensitive potassium channels, thus inducing glucose-independent insulin release by the β-pancreatic cells. The wide variability reported in SU responses has been attributed to the polymorphisms of CYP2C9. The present study aimed to describe CYP2C9 polymorphisms (*2, *3 and IVS8-109T) within a sample of Mexican patients with DMT2, while suggesting the potential clinical implications in terms of glibenclamide response variability. From a sample of 248 patients with DMT2 who initially consented to be studied, those ultimately included in the study were treated with glibenclamide (n=11), glibenclamide combined with metformin (n=112) or metformin (n=76), and were subsequently genotyped using a reverse transcription-quantitative polymerase chain reaction (PCR), end-point allelic discrimination and PCR amplifying enzymatic restriction fragment long polymorphism. Clinical data were gathered through medical record revision. The frequencies revealed were as follows: CYP2C9*1/*1, 87.5%; *1/*2, 6.5%; *1/*3, 5.2%; and CYP2C9, IVS8-109A>T, 16.1%. Glibenclamide significantly reduced the level of pre-prandial glucose (P<0.01) and the percentage of glycated hemoglobin (%HbA1c; P<0.01) for IVS8-109A>T compared with combined glibenclamide and metformin treatment. Concerning the various treatments with respect to the different genotypes, the percentages obtained were as follows: Glibenclamide A/A, HbA1c<6.5=33.3%; glibenclamide + metformin A/A, HbA1c<6.5=24.6%; glibenclamide A/T, HbA1c<6.5=33.3%; glibenclamide + metformin A/T, HbA1c<6.5=25%; glibenclamide T/T, HbA1c<6.5=100%; and glibenclamide + metformin T/T, HbA1c<6.5=12.5%. Altogether, these results revealed that, although genetically customized prescriptions remain a desirable goal to increase the chances of therapeutic success, within the studied population neither allelic variants nor dosages demonstrated a clear association with biomarker levels. A key limitation of the present study was the lack of ability to quantify either the plasma concentrations of SU or their metabolites; therefore, further, precise experimental and observational studies are required.

Cost-effectiveness analysis of pharmacogenomics-guided clopidogrel treatment in Spanish patients undergoing percutaneous coronary intervention.

Clopidogrel is an antiplatelet drug given to patients before and after having a percutaneous coronary intervention (PCI). Genomic variants in the CYP2C19 gene are associated with variable enzyme activities affecting drug metabolism and hence, patients with reduced or increased enzymatic function have increased risk of bleeding. We conducted a cost-effectiveness analysis to compare a pharmacogenomics versus a non-pharmacogenomics-guided clopidogrel treatment for coronary artery syndrome patients undergoing PCI in the Spanish healthcare setting. A total of 549 patients diagnosed with coronary artery disease followed by PCI were recruited. Dual antiplatelet therapy was administrated to all patients from 1 to 12 months after PCI. Patients were classified into two groups: the Retrospective group was treated with clopidogrel based on the clinical routine practice and the Prospective group were initially genotyped for the presence of CYP2C19 variant alleles before treatment with those carrying more than one CYP2C19 variant alleles given prasugrel treatment. We collected data on established clinical and health outcome measures, including, per treatment arm: the percentage of patients that suffered from (a) myocardial infraction, (b) major bleeding and minor bleeding, (c) stroke, (d) the number of hospitalization days, and (e) the number of days patients spent in Intensive Care Unit. Our primary outcome measure for the cost-effectiveness analysis was Quality Adjusted Life Years (QALYs). To estimate the treatment cost for each patient, individual data on its resource used were combined with unit price data, obtained from Spanish national sources. The analysis predicts a survival of 0.9446 QALYs in the pharmacogenomicsarm and 0.9379 QALYs in the non-pharmacogenomics armwithin a 1-year horizon. The cumulative costs per patient were €2971 and €3205 for the Prospective and Retrospective groups, respectively. The main cost driver of total cost in both arms was hospitalization costs. The incremental cost-effectiveness ratio (ICER) was negative indicating that the PGx was a dominant option. Our data show that pharmacogenomics-guided clopidogrel treatment strategy may represent a cost-effective choice compared with non-pharmacogenomics-guided strategy for patients undergoing PCI.